How to create a people picker type metadata in a document set?

Hi folks,

I want to create a people picker type metadata in a document set (it has some content types and it resides inside a library). So please help me knowing steps for creating it. 

Our web application is using classic based authentication therefore I want to retrieve the names and groups in people picker column from Active Directory.

Also, the document set library for which I want to create people picker metadata did not had document set before and documents where saved directly in content types as well as the metadata that now we are making as people picker was before of type Single line of text. 

So, whether after creating it of type people picker, at the time of moving documents into document set, it will create problem? If yes,than of of what kind and how can it be resolved?

Replies will be greatly appreciated.

-Ishita